The chairs are a good match. Leather is probably best, great for kids' spills and accidents, but any fabric will do. Not sure on purple with green - those two colours together clash a bit for me. The green kitchen looks great, and I'm a fan of dark wood. The only thing throwing it off at the moment is the yellowish coloured walls. If they were repainted a soft white, this would make the green and the dark wood really pop, giving you a fresh and sophisticated, calm look which I think would work well. You could then upholster in a green to match the kitchen which would look appealing. Finish it off by some fresh white flowers as accents in the room to draw the eye and you've got a beautifully transformed space with a fabulous feature dining area :)

Also take a look at Room and Board....they have several tables with different wood finishes or wood/steel/metal bases and a good selection of various tabletop materials. Also if you prefer a wood table, an area rug underneath the table could also help to break up all of the wood too.

I would wait for the rug, until you have the shutters up and your furniture placed..it may take on a character of its own and you'll want to compliment. My first thought though was to coordinate with your kitchen and incorporate some black, with a black/beige stripped rug, which would be fun with the wallpaper and perhaps paint your chairs black, add the shutters and you could paint the window trim black and add a large black chandelier.

When you're doing lighting in a kitchen it's a good idea to have good directed light over the main tasks areas, cooking, dishwashing, food prep. You could achieve this with downlights directed at those areas, or track lighting where you can direct/angle each of the lights on the track. Re the pendant over sink area, would need to be at a height that ensures safety - water & electricity, not a good combo. There may be some NZ standards that you can refer to, to get the correct info.